is it possible to cast int into custom class type(in java)? if yes then how?

Question

I am beginner in java, trying to create an abstract method abstract int area() of a abstract class Shape, the Shape class extended on three other classes and overridden area method of these class are calculating area and returns int value and i want to store in Shape class array.

import java.util.Scanner;
abstract class Shape{
abstract int area();
}

class Ractangle extends Shape {
    private int length,width;
    public Rectangle(){
        System.out.println("Enter length rectangle ");
        this.length = Test.scan.nextInt();
        System.out.println("Enter width rectangle ");
        this.width = Test.scan.nextInt();
    }
    public int area(){
    return length*width;
    }
}

class Square extends Shape{
    private int side;
    public Square(){
        System.out.println("Enter side square ");
        this.side = Test.scan.nextInt();
    }
    public int area(){
        return side*side;
    }
}
class Parlellogram extends Shape{
    private int base,height;
    public Parallelogram(){
        System.out.println("Enter base parallelogram");
        this.base = Test.scan.nextInt();
        System.out.println("Enter height parallelogram ");
        this.height = Test.scan.nextInt();
    }
    public int area(){
        return base*height;
    }
}
class Test{
    public static Scanner scan;
    public static void main(String[] args){
        scan = new Scanner(System.in);
        Rectangle rect = new Rectangle();
        Square sq = new Square();
        Parallelogram prlg = new Parallelogram();

        Shape[] shapeArray = {rect.area(), sq.area(), prlg.area()}; //error here

        //shapeArray[0] = rect.area();
        //shapeArray[1] = sq.area();
        //shapeArray[2] = prlg.area();
    }
}

error: incompatible types: int cannot be converted to Shape

Florian Weimer · Accepted Answer · 2017-07-21 14:29:33Z

2

Did perhaps mean to write this?

int[] shapeArray = {ract.area(), sq.area(), prlg.area()};

Or tihs?

Shape[] shapeArray = {ract, sq, prlg};

If you compute the area of a shape, you no longer have a Shape, but an int.

answered Jul 21, 2017 at 14:29

Florian Weimer

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Comments

Vadym Pechenoha · Accepted Answer · 2017-07-21 14:32:22Z

1

Java - is a statically typed language. That means that you cannot store int values inside of the array of Shape. In order to resolve the issue, you should create an array of integers:

int[] shapeArray = { ract.area(), sq.area(), prlg.area() };

answered Jul 21, 2017 at 14:32

Vadym Pechenoha

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KhAn SaAb · Accepted Answer · 2017-07-21 14:35:39Z

1

Exception itself says about issue int cannot be converted to Shape, change the array data type

 int[] shapeArray = {ract.area(),sq.area(),prlg.area()};

the reason is area() method returning value of type int not shape.

edited Jul 21, 2017 at 14:35

answered Jul 21, 2017 at 14:29

KhAn SaAb

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Comments

sschrass · Accepted Answer · 2017-07-21 14:47:14Z

0

Your Shape[] is an array of shapes (just rename shapeArray to shapes and you'll see it) but you are trying to put areas in it.

So from an design point of view, if those are areas, it should be Shape[] areas. Because an area is not a Shape your array needs to be of the type, the areas are, that is int[] areas.

So this should be

int[] areas = {rect.area(), sq.area(), prlg.area()};

Also, try more sophisticated types like List<T>

List<Integer> areas = new List<>() {{
    add(ract.area());
    add(sq.area());
    add(prlg.area());
}};

answered Jul 21, 2017 at 14:47

sschrass

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Comments

arkantos · Accepted Answer · 2017-07-21 14:56:44Z

0

You are trying to put primitive type(int) in an array of an object type(Shape), which is illegal.

If you meant to "put area values in an array", you have to create an array of type int. Please do the following;

int[] areaArray = {ract.area(),sq.area(),prlg.area()};

answered Jul 21, 2017 at 14:56

arkantos

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